As for a conventional mechanical seal of the water pump suitable for the coolant pump or so of the car engine, for example, the mechanical seal disclosed in published Japanese patent application No. 2000-74226 (Patent Document 1) may be mentioned. The mechanical seal disclosed in the patent document 1 comprises a constitution as shown in the cross sectional structure of FIG. 8. That is, a mating ring 11 is engaged and fixed to the sleeve 13 via a cup gasket 12, and rotates along with a rotation axis 2. A seal ring 14 which slides with respect to the mating ring 11 is engaged in the cartilage 96 which engages with a pump housing 3, along with a bellows 15, a case 17, a driving band 19 and a coiled wave spring 18. Then, the seal ring 14 is pressed against mating ring 11 by the biasing force of the bellows 15 and the coiled wave spring 18, and the appropriate surface pressure is applied to the sliding face between these, thus performs appropriate sealing.    Patent Document 1: Published Japanese patent application No. 2000-74226